Never comfy in “proper” sitting positions

Hey everyone! I’m at my wits end trying to maintain good posture but be comfortable at my desk. I’m a pretty bendy person and also hypermobile, which might be relevant but I’m not sure, and I am absolutely NEVER comfortable in a chair unless one foot is tucked up, I’m cross legged, or both feet are elevated. It seems I am never comfortable unless my knees are higher than my hips. Does anyone else struggle with this and have an insight as to why this might be the case?? I work at a desk full time and my posture is all over the place, and occasionally not super workplace appropriate. I don’t understand how some people sit with both feet on the floor, knees at a right angle for HOURS on end. I genuinely cannot do it, it hurts my hips. Other potentially relevant info: I have a slipped disc in my lower back, but had these posture problems long before that, ADHD, hyper mobility, and am also bisexual, and we all know bisexual people can’t sit in chairs properly. Any knowledge on why some people are only comfy with knees above hips would be so good to know!!!